Treatment of tall oil fatty acids



United States Patent TREATMENT OF TALL OIL FATTY ACIDS Charles S. Nevin,Stamford, Conn., assignor to American Cyanamid Company, New York, N. Y.,a corporation of Maine No Drawing. Application July 27, 1955, Serial No.524,801

6 Claims. (Cl. 260--97.5)

This invention relates to methods of improving the drying properties oftall oil fatty acid mixtures containing low percentages of rosin acidsand more particularly is concerned with methods of improving the dryingproperties, color and odor of tall oil fatty acid mixtures from whichsubstantially all or at least a major proportion of the rosin acids havebeen removed.

Tall oil is a mixture consisting primarily of (l) rosin acids related tothe abietic acids and (2) fatty acids for the most part oleic andlinoleic acids. It is obtained as a by-product in the manufacture ofkraft paper by the sulfate process. In this process, chips of pine woodare digested under heat and pressure with a solution of sodium hydroxideand sodium sulfide in order to free the cellulose of other woodconstituents. The highly alkaline solution forms soluble sodium soaps ofthe lignin and rosin and of the fatty acids originally present asesters. These are washed out of the wood pulp as a dark solution, knownas black liquor, which is concentrated, cooled and allowed to standwhereby fatty acid and rosin soaps separate out as a dark brown, curdymass called black liquor soap. This black liquor soap is skimmed off andis boiled with sulfuric acid to convert the sodium soaps into free rosinand fatty acids. The reaction mixture is allowed to settle and theclear, brown, crude tall oil separates out and may be collected.

Crude tall oil comprises a mixture of rosin and fatty acids and isnormally clear, dark brown oil containing from about 35 to about 55% byWeight of rosin acids and from about 60 to about 40% by weight of fattyacids, plus from about 5 to about by weight of other constituents,primarily unsaponifiables and materials of unestablished chemicalidentity.

Crude tall oil is ideal for applications where rosin acids and fattyacids can be used together and are employed in many commercial instancessuch as in the paint and varnish industries in applications where theirdark color or other restrictions do not prohibit their use.

Distilled and fractionated tall oil products with reduced amounts ofrosin acids are commercially available. Their composition ranges fromabout 20 to about 35% by Weight of rosin acids and from about 80 toabout 65% by weight of fatty acids, plus from about 1 to about 5.5% byweight of unsaponifiables and other materials. These products arelight-colored and are excellent for industrial applications in thepaint, enamel and varnish industries, having excellent dryingproperties, color and odor.

More highly fractionated products from which substantially all or atleast a major portion of the rosin acids have been removed are alsocommercially available. Such products may comprise, for example, fromabout 1 to about 12% by weight of rosin acids and from about 83 to about98% by weight of fatty acids, plus from about 1 to about 5% by weight ofunsaponifiables and other materials. These products are even lightercolored, have a relatively good odor but, due to their low rosin acidcontent, do not possess the fast drying properties possessed by the lessfractionated mixtures having a higher rosin acid content.

Inasmuch as such more highly fractionated products containing lowerpercentages of rosin acids are more desirable from a color retention andflexibility standpoint but are less desirable from a drying standpoint,it is a principal purpose of the present invention to improve theirdrying properties to render them more desirable from both standpointsand consequently of more widespread industrial application.

Attempts have hitherto been made to remove the interfering constituentsresponsible for the poor drying qualities of such refined tall oil fattyacid. products containing low amounts of rosin acids but such attemptshave been either unsuccessful or uneconomical. Such prior attempts haveincluded, for example, fractional distillation, extraction of the soapswith selected solvents, extraction of the free acids with furfural,extraction with propane by the Solexol process and separation by lowtemperature crystallization.

it has now been found that, if these tall oil fatty acid productscontaining from about 1 to about 12% by weight of rosin acids and fromabout 83 to about 98% by weight of fatty acids, plus from about 1 toabout 5% by weight of unsaponifiables and other interfering materials,are treated by the combined processes of the present invention, theinterfering materials are removed and/or modified and the treatedproducts possess vastly improved drying characteristics.

More specifically, it has now been found that, if these tall oil fattyacid products containing negligible or low amounts of rosin acids aretreated with metallic zinc, the zinc apparently reacts with the fattyacids to release hydrogen and thus creates reducing conditions whichaffeet the nature and properties of the undesirable natural antioxidantsor interfering materials (particularly, the boiling points thereof)whereby a simple distillation may be employed to separate them from thedesired tall oil fatty acid mixture.

Additionally, it is believed that the zinc or the zinc tallate which isformed acts presumably somewhat as catalyst to promote polymerization orcondensation re actions of such interfering materials to change theirproperties whereby they are rendered non-volatile under conditions oftemperature and pressure wherein the tall oil fatty acid mixture isvolatile and may be separated by a simple distillation.

Such conditions and reactions, however, do not ap parently affect thetall oil fatty acids to any substantial degree inasmuch as the productcoming over during the distillation is similar to the original materialexisting prior to the zinc treatment, the sole difference being theremoval of the interfering anti-drying bodies.

Experimentation proved that simple distillation of the tall oil fattyacids without prior zinc treatment does not alter the composition, theappearance, or the drying properties of the tall oil fatty acids.

While as little zinc as 0.05% by weight of the tall oil fatty acids showsome improvement in the drying properties, it is preferable to use fromabout 0.1% to about 0.5% by weight of the zinc. In general, however,amounts ranging up to about 1 or 2% may be used effectively, with largeramounts up to 5%, for example, presenting no material advantage.

The line is preferably added in a finely divided form such as zinc dustor zinc powder. However, zinc in any other desirable form may also beused as, for example, mossy zinc, zinc turnings or granular zinc.

The temperature used for treatment of acid mixture with metallic zinc200 to about 235 the tall oil fatty is preferably from about (3., buttemperatures ranging from 150-250 C. are effective within the broaderaspects of the present inventive concept. The pressure maintained duringthe treatment of the tall oil fatty acid mixture is preferably normalatmospheric pressure but it is to be appreciated that subatmospheric orsuperatmospher ic pressures may be used with corresponding changes intemperatures.

The time required for the zinc treatment of the tall oil will varydepending upon the temperature, the quantity of the anti-dryingcompounds, color bodies and odoriferous material present in the talloil, the degree of agitation. the rate of bubbling of the inert gasthrough the liquid if an inert gas is used in conjunction with the heattreatment in the presence of zinc, etc.

The distillation procedures employed in carrying out the principles ofthe present invention are the simple distillations normally carried outin the industry. Temperatures and pressures are, of course,interdependent and vary within wide related ranges. In the present case,however, it has been found that temperatures of from about 200 to about240 C. and pressures of from about 3 to about 15 mm. are preferred,although lower and higher values are effective, provided the conditionsare such that the tall oil fatty acids are distillable away from theundesirable natural antioxidants and interfering antidrying bodies.

The distillations may also be carried out in the presence of steam or aninert gas such as carbon dioxide, nitrogen, etc., at relatively higherpressures of from about 30 to about 70 mm. or more.

With regard to the interfering materials which prevent the desirabledrying properties of the tall oil fatty acid mixtures and which areremoved by the combined processes of the present invention, it ispresumably believed that they comprise phenolic bodies and otherantioxidants and that they are normally present in amounts of from about0.01% to about 1.0% by weight. Their exact chemical structure andnature, however, has not been established but it has been determinedthat, once they are removed by the combined processes herein describedthe treated tall oil fatty acid mixture containing low percentages ofrosin acids acquires excellent drying properties.

The invention will be further illustrated in greater detail by thefollowing specific examples and evaluations. It should be understood,however, that although these examples may describe in particular detailsome of the more specific features of the present invention, they aregiven primarily for the purpose of illustration and the invention in itsbroader aspects is not to be construed as limited thereto.

In these examples, it is to be stated that the term Acintol FA #1"refers to a singly-fractionated tail oil fatty acid mixtureapproximately comprising 92.5% fatty acids (425% linoleic acid; linoleicacid; 47.2% oleic acid and 2.8% saturated acids), 3.5% rosin acids and4.0% unsaponifiables and other materials. It is also to be stated thatthe term Acintol FA #2 refers to a doubly-fractionated tall oil fattyacid mixture approximately comprising 96.8% fatty acids (46.1% linoleicacid; 0% linolenic acid; 48.4% oleic acid and 2.1% saturated acids),1.0% rosin acids and 2.2% unsaponifiables and other materials. Thesepercentages, as are all other percentages referred to herein, are byweight based on the total weight of the completed acid mixture, unlessotherwise indicated.

The Hours to Reach system referred to in the following tests is based onthe number of hours required for the film to obtain the described filmcharacteristics. Under test conditions in an air-conditioned room at 77F. (12 F.) and 50% (i4%) relative humidity, (1) Dust Free indicates thata finger may be drawn lightly over the film without leaving a mark, (2)Set to Handle indicates that finger marks produced by light pressure maybe removed by gently polishing, (3) Light Tack indicates a light tackyfeeling as obtained by a 50 gram- 4 5 second Tack test results and (4)Tack Free indicates the complete absence of tack as obtained by a 300gram weight-5 second Tack test result (ASTM-D 15450 T-p. 61).

EXAMPLE 1 A sample of tall oil fatty acids containing 1.2% rosin acids,2.4% unsaponifiables, 5.0% conjugated linoleic acids, and 42.5% totallinoleic acids was heated under an atmosphere of nitrogen to 235 C. Tothe hot fatty acids, 0.3% of zinc dust based on the weight of the fattyacids present was added and the mixture was stirred for 30 minutes whilemaintaining the temperature at 235 C. During the reaction some of thezinc dust particles agglomerated. By discontinuing the stirring, thisunreacted zinc immediately settled and was readily separated from thefatty acids. The fatty acids were distilled at 220- 235 C. and 10 mm. Hgpressure giving a yield of 97% product and 3% residue. The treated fattyacids product contained 0.9% rosin acids, 2.2% unsaponifiables, 4.5%conjugated linoleic acids, and 40.7% total linoleic acids.

EXAMPLE 2 A sample of Acintol FA #2 tall oil fatty acids was heatedunder an atmosphere of nitrogen to 235 C. To the hot fatty acids, 0.3%of zinc dust was added and the mixture was stirred for 30 minutes whilemaintaining the temperature at 235 C. During the reaction some of thezinc dust particles agglomerated. By discontinuing the stirring, thisunreacted zinc immediately settled and was readily separated from thefatty acids. The fatty acids were distilled at 220-235 C. and 10 mm. Hgpressure giving a yield of 97.1% product and 2.9% residue. The treatedfatty acids product contained 1.0% rosin acids, 2.2% unsaponifiables,4.5% conjugated linoleic acids, and 46% total linoleic acids. Dryingtime evaluations for the treated and untreated fatty acids are shown infollowing examples.

EXAMPLE 3 A sample of Acintol FA #2 tall oil fatty acids was heatedunder an atmosphere of nitrogen to 215 C. To the hot fatty acids, 0.2%of zinc dust was added and the mixture was stirred for 60 minutes whilemaintaining the temperature at 215 C. During the reaction some of thezinc dust particles agglomerated. By discontinuing the stirring, thisunreacted Zinc immediately settled and was readily separated from thefatty acids. The fatty acids were distilled at 220235 C. and 10 mm. Hgpressure giving a yield of 96.5% product and 3.5% residue. The treatedfatty acids product contained 1.0% rosin acids, 2.2% unsaponifiables,4.8% conjugated linoleic acids, and 45% total linoleic acids.

EXAMPLE 4 were distilled at 220235 C. and 10 mm. Hg pressuregiving ayield of 96.8% product and 3.2% residue. The

treated fatty acids product contained 3.2% rosin acids, I

3.8% unsaponifiables, 4.1% conjugated linoleic acids, and 40.7% totallinoleic acids. Drying time evaluations for the treated and untreatedfatty acids are shown in following examples.

EXAMPLE 5 To determine the effect of the zinc treatment on the dryingproperties ofthe tall oil fatty acids, drying rates were" evaluated forwhite, air-drying enamels made from treated tall oil fatty acids anduntreated tall oil fatty acids and a commercially available rapid dryingexpensive distilled fatty acid mixing having an approximate compositionof 54% linoleic acid, 40% oleic, 2% linolenic acid and 4% saturatedfatty acids.

Enamel composition Vehicle: Long oil alkyd--23.4% phthalic anhydride,19.2% pentaerythritol, and 57.4% fatty acids specified. Pigment/binder:100/ 100 (TiOz pigment) Drier:0.4% lead and 0.04% cobalt Thinner: Varsol#1 to 70 Krebs units Film thickness 0.0015 inch wet films on glass Hoursto reach description Acintol Aeintol Commer- Film Description FA 2 FA 2cial Untreated, Zinc Fatty ours Treated, Acids, ours hours Dust Free- 42 1. 5 Set to Handle 6 3 2. 5 Light Tack. 7 3. 5 3 Tack Free 24 6 6EXAMPLE 6 In this example, drying evaluations for alkyd clears preparedfrom the specified fatty acids are presented.

Alkyd clear composition 1) 23.4% phthalic anhydride (2) 19.2%pentaerythritol (3) 57.4% fatty acids specified 70% of (1)+(2)+(3) inVarso1#1 Alkyd composition reduced to 50% nnvolatile.

Drier: 0.4% lead; 0.04% cobalt. Film thickness: 0.0015 inch wet films onglass.

Hours to reach description Acintol Acintol Commer- FA 2 FA 2 cial FilmDescription Untreated, Zinc Fatty ours Treated Acids, hours hours DustFree 4 2. 2. 5 Set to Handle--. 6 3 3 Light Tack 8 4 3.5 Tack Free 24 87 EXAMPLE 7 The procedures of Example 6 were carried out substantiallyas set forth therein with the sole exception that Acin- 6 tol FA 1 wasused instead of Acintol FA 2. The evaluations were as follows:

Although I have described specific examples of my inventive concept andseveral tests thereof, as well as the chemical and physicalcharacteristics of particular samples thereof, I consider the same notto be limited to the specific substances mentioned therein but toinclude various other compounds of equivalent constitution as set forthin the claims appended hereto. It is understood, of course, that anysuitable changes, modifications and variations may be made withoutdeparting from the spirit and scope of the invention.

What I claim is:

l. A method of improving the drying properties of a tall oil fatty acidmixture containing from about 1 to about 12% by weight of rosin acidsand from about 0.01 to about 1% by weight of slow-drying interferingmaterials which comprises heating the mixture with metallic zinc in anamount from about 0.05 to about 2.0% by Weight of said mixture at atemperature of from about to about 250 C. and distilling the resultingmixture to separate and leave behind slow-drying interfering materialsto obtain a tall oil fatty acid mixture possessing improved dryingproperties.

2. A method as defined in claim 1 wherein the metallic zinc is presentin an amount from about 0.1 to about 0.5% by weight of the mixture.

3. A method as defined in claim 1 wherein the mixture is heated at atemperature of from about 200 to about 235 C.

4. A method of improving the drying properties of a tall oil fatty acidmixture containing from about 1 to about 12% by weight of rosin acids,from about 83 to about 98% by weight of fatty acids and from about 0.01to about 1% by weight of slow-drying interfering materials whichcomprises heating the mixture with metallic zinc in an amount from about0.1 to about 0.5 by weight of said mixture at a temperature of fromabout 200 to about 235 C. and distilling the resulting mixture toseparate and leave behind the slow-drying interfering materials toobtain a tall oil fatty acid mixture possessing improved dryingproperties.

5. A method as defined in claim 4 wherein said distillation takes placeat a temperature of from about 200 to about 240 C. at a presssure offrom about 3 to about 15 mms.

6. A method as defined in claim 4 wherein said distillation is carriedout in the presence of a member of the group consisting of steam andinert gas.

No references cited.

1. A METHOD OF IMPROVING THE DRYING PROPERTIES OF A TALL OIL FATTY ACIDMIXTURE CONTAINING FROM ABOUT 1 TO ABOUT 12% BY WEIGHT OF ROSIN ACIDSAND FROM ABOUT 0.01 TO ABOUT 1% BY WEIGHT OF SLOW-DRYING INTERFERINGMATERIALS WHICH COMPRISES HEATING THE MIXTURE WITH METALLIC ZINC IN ANAMOUNT FROM ABOUT 0.05 TO ABOUT 2.0% BY WEIGHT OF SAID MIXTURE AT ATEMPERATURE OF FROM ABOUT 150* TO ABOUT 250* C. AND DISTILLING THERESULTING MIXTURE